Question

EAN of Mn in $M{{n}_{2}}{{(CO)}_{10}}$is:
(a).33
(b).34
(c).35
(d).36

Answer 1

Hint: Efficient Atomic Number (EAN), number representing the total number of electrons in a metal complex surrounding the nucleus of a metal atom. It is composed of electrons from the metal atom and the bonding electrons from the electron-donating atoms and molecules surrounding it.

Complete answer:
Ligand, in chemistry, in a coordination or complex compound, any atom or molecule attached to a central atom, typically a metallic element. The atoms and molecules used as ligands are almost all those capable of acting as the electron-pair donor in the electron-pair bond formed with the metal atom (a covalent coordinate bond). Popular ligands are examples of the neutral molecules water (${{H}_{2}}O$), ammonia ($N{{H}_{3}}$), and carbon monoxide ($CO$) and the anions cyanide ($C{{N}^{-}}$), chloride ($C{{l}^{-}}$), and hydroxide ($O{{H}^{-}}$).
 In the given compound Manganese Atomic number is 25 and as ($CO-CO$) Carbon monoxide is a neutral ligand so Manganese oxidation state is zero. Also, the number of electrons provided by each $CO$ ligand is 2.
So, the EAN = metal electrons + ligand-donated electrons + 1 M-M $\Delta $bond.
EAN = 25 + 1 + 10=36 per Mn.

So, choice D is the right one.

Additional information:
A chemical element's atomic number, or proton number, is the number of protons found in the nucleus of each atom of that element. A chemical element is uniquely identified by atomic number. It is identical to the nucleus charge number.

Note:
The oxidation state, often referred to as the oxidation number, describes the degree of oxidation of an atom in a chemical compound (loss of electrons). Conceptually, the oxidation state, which may be positive, negative, or zero, is the hypothetical charge an atom would have if all bonds to atoms of various elements were 100 percent ionic, with no covalent component. This is never exactly the case for real bonds.